Abstract:

Objective To study the molecular epidemiologic characteristics of the main epidemic strains and the imported strains of M.tuberculosis complex (MTBC) at Guangdong port.Methods Five hundred and fifty-eight MTBC strains preserved at Guangdong port were genotyped by melting curve spoligotyping (McSpoligotyping). The spoligotype patterns were compared with SITVITWEB database to obtain spoligotype international type (SIT) number and clustered by BioNumerics 7.6 version.Results Five hundred and fifty-eight MTBC strains were divided into 107 spoligotype patterns, among which 66 patterns belonged to 8 families and 4 lineages. Lineage 2 and lineage 4 were accounted for 86.38% (482/558) of the total strains. SIT1, SIT53, SIT52, SIT50, SIT190 and SIT19 were the six main epidemic clusters, among which SIT1 was the biggest one. The 17 imported MTBC contained Beijing, Latin American and Mediterranean (LAM), East African Indian (EAI), T, Africanum (AFRI) as well as undefined gene family, including 23.53% (4/17) new genotypes. No significant difference was observed between Beijing family strains (27.25%, 106/389) and non-Beijing family strains (23.81%, 40/168) in drug resistance (χ ²=0.72, P=0.40). Nevertheless, the drug resistant rate of atypical Beijing family strains (45.83%, 11/24) was higher than that of typical Beijing family strains (26.03%, 95/365), and the differences were significant (χ ²=4.46, P=0.03).Conclusion Lineage 2 and lineage 4 of MTBC are the main epidemic strains at Guangdong port. The imported strains are dominated by gene families prevalent in the source areas and new genotypes. It’s necessary to strengthen the molecular epidemiologic surveillance of the main epidemic strains and the imported strains. There is a correlation between atypical Beijing family strains and drug resistance.

Key words: Mycobacterium, tuberculosis, Oligonucleotide array sequence analysis, Bacterial typing techniques, Genetic testing, Drug resistance, bacterium, Guangdong port